feat: initial commit

Author: madonuko

.gitignore

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+dive

LICENSE

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+MIT License
+
+Copyright (c) 2024 Madonuko, Ultramarine Project, Fyra Labs, Et al.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# dive
+
+A chroot utility (just like `arch-chroot`).

dive.nimble

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+# Package
+
+version       = "0.1.0"
+author        = "madomado"
+description   = "A chroot utility"
+license       = "MIT"
+srcDir        = "src"
+bin           = @["dive"]
+
+
+# Dependencies
+
+requires "nim >= 2.1.1"
+requires "cligen"
+requires "sweet"

src/dive.nim

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+import std/[strutils, strformat, paths, os, dirs, files, osproc]
+import asyncdispatch
+import cligen, sweet
+import log, mounts
+
+let mounteds = getMounts()
+
+proc is_mountpoint(root: Path): bool =
+  for mount in mounteds:
+    if root == mount.mountpoint.Path:
+      return true
+
+proc mkdir(dir: Path) =
+  try: dir.createDir
+  except OSError:
+    error "Cannot create dir: " & dir.string
+    quit 1
+
+proc run(cmd: string) {.async.} =
+  info "Running command: "&cmd
+  let p = startProcess("sh", args=["-c", cmd], options={poParentStreams})
+  while p.running:
+    await sleepAsync 10
+  let rc = p.waitForExit
+  if !!rc:
+    fatal "Fail to execute command: "&cmd
+    fatal "Command returned exit code: " & $rc
+    quit 1
+
+proc force_mountpoint(root: Path) {.async.} =
+  if root.is_mountpoint: return
+  warn fmt"{root.string} is not a mountpoint, bind-mounting…"
+  await run fmt"mount --bind {root.string.quoteShell} {root.string.quoteShell}"
+
+proc mount(path: Path, mountargs: string) {.async.} =
+  if !path.is_mountpoint:
+    mkdir path
+    await run "mount "&mountargs&" "&path.string
+
+proc mount_dirs(root: Path) {.async.} =
+  await mount(root/"proc".Path, "-t proc proc") and
+    mount(root/"sys".Path, "-t sysfs sys") and
+    mount(root/"dev".Path, "-o bind /dev") and
+    mount(root/"dev/pts".Path, "-o bind /dev/pts")
+
+proc cp_resolv(root: Path) {.async.} =
+  if !"/etc/resolv.conf".Path.fileExists:
+    warn "/etc/resolv.conf does not exist"
+    return
+  let dest = root/"etc/resolv.conf".Path
+  if !dest.fileExists:
+    warn "Refusing to copy resolv.conf because it doesn't exist inside chroot"
+    return
+  await run "mount -c --bind /etc/resolv.conf "&dest.string
+
+proc umount(path: string) {.async.} =
+  try: await run fmt"umount {path}"
+  finally: discard
+
+proc umount_all(root: string) {.async.} =
+  await umount(fmt"{root}/proc") and
+    umount(fmt"{root}/sys") and
+    umount(fmt"{root}/dev {root}/dev/pts") and
+    umount(fmt"{root}/etc/resolv.conf")
+
+proc find_shell(root: Path): string =
+  if fileExists root/"bin/fish".Path:
+    return "/bin/fish"
+  if fileExists root/"bin/zsh".Path:
+    return "/bin/zsh"
+  if fileExists root/"bin/bash".Path:
+    return "/bin/bash"
+  if fileExists root/"bin/sh".Path:
+    return "/bin/sh"
+  warn "Cannot detect any shell in the chroot… falling back to /bin/sh"
+  "/bin/sh"
+
+proc dive(args: seq[string], verbosity = lvlNotice, keepresolv = false) =
+  ## A chroot utility
+  if !args.len:
+    fatal "You must provide an argument for the root directory"
+    quit 1
+  let root = args[0].Path
+  let cp_resolv_fut = cp_resolv root
+  waitFor (force_mountpoint root) and (mount_dirs root) and cp_resolv_fut
+  waitFor cp_resolv_fut
+  let shell = find_shell root
+  let str_args = args[1..^1].join(" ")
+  waitFor run fmt"SHELL={shell} chroot {root.string} {str_args}"
+  waitFor umount_all(root.string)
+
+
+dispatch dive, help = {
+  "args": "<root directory> [shell command]",
+  "verbosity": "set the logging verbosity: {lvlAll, lvlDebug, lvlInfo, lvlNotice, lvlWarn, lvlError, lvlFatal, lvlNone}",
+}, short = {"keepresolv": 'r'}

src/log.nim

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+import std/logging
+
+var logger = newConsoleLogger(fmtStr="mkfstab: $levelname: ", useStderr=true)
+addHandler logger
+
+export debug, error, fatal, info, log, notice, warn, logging

src/mounts.nim

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+import std/[streams, strformat, strscans]
+import log
+
+type Mount* = tuple[device: string, mountpoint: string, fstype: string, mountopts: string]
+
+proc notSpace(input: string, match: var string, start: int): int =
+  result = 0
+  while input[start+result] != ' ': inc result
+  match = input[start..start+result-1]
+
+
+proc getMounts*(): seq[Mount] =
+  var fdmounts = newFileStream("/proc/mounts")
+  if fdmounts == nil:
+    # cannot open file
+    return @[]
+  defer: fdmounts.close()
+  var linenum = 0
+  var line, dev, mp, fstype, mountopts: string
+  while fdmounts.readLine line:
+    inc linenum
+    if scanf(line, "${notSpace} ${notSpace} ${notSpace} ${notSpace} 0 0$.", dev, mp, fstype, mountopts):
+      result.add (device: dev, mountpoint: mp, fstype: fstype, mountopts: mountopts)
+    else:
+      error fmt"Fail to parse /proc/mounts:{linenum} : {line}"